CVE-2026-63379
MEDIUMDescription
Libevent is an event notification library. Prior to 2.1.13 and 2.2.2-alpha, libevent processes chunked HTTP trailers in http.c through evhttp_read_trailer and merges them into request headers. The fix introduces evhttp_parse_headers_impl_ and a temporary trailer header list. An unauthenticated remote attacker can place security-sensitive fields in trailers so that an upstream proxy and the libevent application interpret different effective headers, enabling header smuggling, authorization bypass, proxy-header spoofing, or cache poisoning. The fix parses trailers into a temporary header list and discards them instead of merging them into req->input_headers. This issue is fixed in versions 2.1.13 and 2.2.2-alpha.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v4 Vector
Exploitability
Impact
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Exploit Intelligence
Moderate risk: more likely to be exploited than 42% of all known CVEs.
References
Related Vulnerabilities
Other CWE-444 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2022-22536 | Critical | 10.0 | 98% | KEV | - |
| CVE-2025-61884 | High | 7.5 | 98% | KEV + Ransom | - |
| CVE-2020-9490 | High | 7.5 | 89% | - | Fix |
| CVE-2023-41265 | Critical | 9.6 | 88% | KEV + Ransom | - |
| CVE-2023-25690 | Critical | 9.8 | 85% | - | Fix |
| CVE-2022-32214 | Medium | 6.5 | 81% | - | Fix |
Common questions
How do I fix CVE-2026-63379?
Published advisories record a fix for 3 affected products. The "How to fix" section on this page lists the fixed version and source advisory for each one, so apply the entry matching what you actually run.
Is CVE-2026-63379 being actively exploited?
Not that we know of. CVE-2026-63379 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.52% is the estimated probability that it will be exploited in the next 30 days. That is higher than 42% of all scored CVEs.
How severe is CVE-2026-63379?
CVE-2026-63379 has a CVSS v4 base score of 6.3, rated moderate. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-63379 affect?
Published advisories record a fix for libevent (Debian), libevent (Red Hat / RHEL), libevent (Rocky). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
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Markdown
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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-08-25.